The present invention relates to an electric connection structure between an integrated circuit (IC) device and a printed circuit board, and in particular, to a structure of a test socket for testing an integrated circuit.
An integrated circuit fabricated through complicated processes is subject to various electric tests for a characteristics measurement or quality inspection. In this respect, a socket is frequently used in order to electrically connect a test circuit of a printed circuit board installed at a test equipment to an external terminal (outer lead) of the IC device. That is, for testing the IC device, the socket serves as an interface for electrically connecting the printed circuit board of the test equipment and an IC device.
A conventional test socket structure will now be described with reference to accompanying drawings.
Generally, as shown in FIG. 1, a test socket of an IC device includes a socket housing 10 and a plurality of contact fingers (contact terminals) 11. The contact finger is formed curved in a semicircle shape so as to have a spring elastic force by a downward pressing pressure. Reference numeral 12 denotes a fixing pin for fixing the IC device so that the electrical connection between the contact finger and the outer lead of the semiconductor device is not be unstable while the IC device is being tested.
FIG. 2 shows a device under test (DUT) 14 as mounted on the socket. The device under test 14 is mounted on the socket in a manner that an outer lead 15 of the device under test 14 is contacted by an upper terminal 11a of the contact finger 11. For performing the test, the lower terminal 11b of the contact finger 11 is mounted to be necessarily contacted on a printed circuit (not shown) of the printed circuit board of the test equipment.
Thereafter, the device under test 14 is pressed down by a pressing unit (not shown), so that the outer lead of the device under test and the upper terminal 11a of the contact pin of the socket are electrically connected by the press-down contact, and the lower terminal 11b of the contact pin and a circuit pattern (not shown) formed on the surface of the board of the test equipment are also electrically connected by the press-down contact.
The device pressing unit (not shown) renders the overall outer leads of the device under test mounted on the socket to be contacted to the upper terminal of the contact fingers, and at this time, the downward pressure has a great value. Accordingly, if such a strong downward pressure is applied thereto in every testing, the frequency of the testing becomes higher, resulting in that the spring elastic force of the contact finger of the socket is deteriorated or there possibly occurs difference in spring elastic force with respect to each contact finger.
With those problem occurring, eventually, a contact finger having a weakened spring elastic force among the plural contact fingers would cause a contact inferiority or a contact instability over such connection between the device under test and the external terminal, even though the device under test is pressed down by the pressing pressure.
Such a contact finger having the weakened spring elastic force must be replaced by a new normal one. In this respect, in case of a socket having the contact finger and the socket housing as an incorporated one, even if there occurs a contact deterioration or contact instability for a single contact finger, the high-priced socket itself needs to be replaced by a new one, which inevitably incurs a heavy expense for testing with a prodigal waste.
In order to resolve such a problem, the U.S. Pat. No. 5,634,801 discloses a test socket having a structure that a defective contact pin is individually replaced, as illustrated in FIGS. 3A and 3B, details of which will now be described.
The socket shown in FIG. 3A includes a housing 30, a plurality of contact pin receiving slots 31 each arranged in parallel at predetermined intervals within the housing 30, an upper and a lower cavities 32a and 32b each formed at an upper surface and a lower surface of the housing. The upper cavity 32a formed at the upper surface of the housing 30 and the lower cavity 32b formed at the lower surface of the housing 30 are positioned at marginal portions in mutually opposite side of the slot.
Elastomer 33a and 33b are respectively installed within the upper and lower cavities 32a and 32b. Inside each of the contact pin receiving slot 31, S-shaped contact pins 34 are respectively inserted, of which an upper end portion and a lower end portion are respectively rested on the elastomers.
Reference numeral 35 denotes a printed circuit board of the test equipment, and reference numeral 36 denotes a circuit pattern formed on the printed circuit board, which is connected to the lower surface of the contact pin 34.
FIG. 3B is a longitudinal-sectional view taken along line IVxe2x80x94IV of FIG. 3A.
As described above, the conventional socket has an advantage in that since each contact pin 34 is individually installed in each contact pin receiving slot 31, any defective contact pin can be replaced by a normal one whenever it occurs.
Nevertheless, it also has disadvantages in the following aspects.
First, in case that plural contact pins 34 are defective, each contact pin should be replaced one by one, causing inconvenience and taking much time for replacing the contact pins.
Secondly, in order to perform testing, when the IC device (not shown) is pressed downwardly (xe2x80x98axe2x80x99 direction) as is mounted on the upper portion of the contact pin, the lower surface portion 34a of the contact pin 34 moves in the horizontal direction to the circuit pattern, that is, in a xe2x80x98bxe2x80x99 direction toward inside the socket, while being contacted with the circuit pattern 36 of the printed circuit board.
In addition, after finishing the testing, when the semiconductor device is raised upward (xe2x80x98cxe2x80x99 direction), the lower surface portion 34a of the contact pin 34 moves in the horizontal direction, that is, xe2x80x98dxe2x80x99 direction opposite to the xe2x80x98bxe2x80x99 direction.
Accordingly, if the testing of the semiconductor device is repeatedly done, the lower surface portion 34a of the contact pin 34 always contacts the circuit pattern 36 whenever it moves in the xe2x80x98bxe2x80x99 and xe2x80x98dxe2x80x99 directions. Consequently, repeated movement of the lower surface portion 34a causes an abrasion on the part of the circuit pattern 36 where the contact pin is continuously contacted thereto, creating a problem of deterioration on the printed circuit board of the high-priced test equipment.
Fabricating method of the contact pin or the contact finger of the conventional test socket is as follows.
As shown in FIG. 4A, a metal plate 40 having straight grains 41 in one direction is formed by extrusion molding. And, As shown in FIG. 4B, a contact pin or contact finger 42 in patterns such as xe2x80x98Cxe2x80x99-shape or xe2x80x98Sxe2x80x99-shape is drawn. And then, as shown in FIG. 4C, a pattern shaped in a contact finger is cut out therefrom, to thereby form a contact finger 42.
In this respect, however, the contact finger made by that method is easily broken along the metal grains during the testing, as up and down movement is repeated by hundreds and thousands of times.
In addition, as the movement in the direction perpendicular to the direction of the metal grain is repeated, its spring elastic force is weakened, so that the contact finger is easily deformed, resulting in that a durability of the socket is shortened.
Therefore, it is an object of the present invention to provide a test socket structure in which a contact pin of a defective socket is replaced by block unit.
Another object of the present invention is to provide a test socket structure in which a pattern of a printed circuit board of a testing equipment is not abraded during testing of a semiconductor device.
Still another object of the present invention is to provide a test socket in which an elastomer is installed at a portion where an end portion of a contact pin contacts a socket housing so as to successively maintain a spring elastic force at the end portion of the contact pin, thereby lengthening a durability of the contact pin, and height deviation of each contact pin is reduced, so that a reliability in an electrical connection between the contact pin and an outer lead of a device under test is obtained.
Yet another object of the present invention is to provide a fabricating method of a contact pin by which the contact pin is hardly deformed and its spring elastic force can be maintained for a long time.
Also, another object of the present invention is to provide a fabricating method of a contact pin for a test socket for which a metal strip cut in a metal grain direction over metal plate is bent or curved in a direction perpendicular to the metal grain direction, so that a socket pin has a strong spring elastic force and is not easily deformed or not easily fatigued.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a test socket including: a first housing made of an insulating material having a predetermined thickness; a second housing made of an insulating material, a side wall of which is adjacent to a side wall of the first housing; a first and a second elastomers respectively installed at an upper and a lower surfaces of the second housing; and a contact pin block having a plurality of contact pins arranged at predetermined pitches and a fixing unit for fixing the plurality of contact pins so that they can be moved together, wherein the contact pin block is insertedly installed between the first and the second housings and is contacted with the first and the second elastomers in the vicinity of both end portions of the contact pin.
The first housing of the test socket of the present invention is the insulating material having an opening at its central portion, while the second housing is an insulating plug insertedly installed at the opening of the first housing.
There is also provided a test socket in accordance with another embodiment of the present invention including: a first housing made of an insulating material having a slit at the central portion of its upper surface and a receiving recess at the central portion of its lower surface; a left supporting unit and right supporting unit respectively insertedly installed within the receiving recess of the first housing; a first elastomer protrusively installed both at a side wall of the left supporting unit and at a side wall of the right supporting unit; a left contact pin block supported by the side wall of the left supporting unit; and a right contact pin block supported by the side wall of the right supporting unit, wherein the left contact pin block and the right contact pin block have respectively at least one bent portion, the contact pins are bent outwardly of each side wall of the left supporting unit and the right supporting unit, and the bent portion of the left contact pin block and that of the right contact pin block are closed to each other.
In order to attain the object of the present invention, there is provided a test socket including: a first housing made of an insulating material having a slit at the central portion of its upper surface and a receiving recess at the central portion of its lower surface; a right supporting unit and left supporting unit respectively insertedly installed within the receiving slot of the first housing; a first and a second elastomers respectively protrusively installed at an upper side and a lower side of each side wall at a predetermined interval; a left contact pin block supported by the side wall of the left supporting unit; and a right contact pin block supported by the side wall of the right supporting unit, wherein the left contact block and the right contact block have two convex bent portions formed convexly in the distanced direction from the side wall and a concave bent portion formed between the convex bent portions and bent in the adjacent direction to the side wall of the supporting unit, and each convex bent portion of the left contact pin block and the right contact pin block closes to each other.
In order to attain the object of the present invention, there is also provided a fabricating method of contact pin block of a test socket including the steps of: preparing a metal plate extrusion molded so as to have grains in a constant direction thereon; cutting the metal plate in the grain direction to form a metal strip; bending or curving the metal strip in a direction perpendicular to the grains to make a contact pin for socket; and arranging the plurality of contact pins at constant pitches and attaching an insulating tape onto one side or both sides of the contact pin to thereby form a contact book.